Simplify the constness checks

Author: oli-obk

src/librustc/dep_graph/dep_node.rs

@@ -479,7 +479,6 @@ define_dep_nodes!( <'tcx>
 
     // Represents the MIR for a fn; also used as the task node for
     // things read/modify that MIR.
-    [] MirConstQualif(DefId),
     [] MirBuilt(DefId),
     [] MirConst(DefId),
     [] MirValidated(DefId),
@@ -562,7 +561,6 @@ define_dep_nodes!( <'tcx>
     [input] DefSpan(DefId),
     [] LookupStability(DefId),
     [] LookupDeprecationEntry(DefId),
-    [] ConstIsRvaluePromotableToStatic(DefId),
     [] RvaluePromotableMap(DefId),
     [] ImplParent(DefId),
     [] TraitOfItem(DefId),

src/librustc/lib.rs

@@ -74,6 +74,7 @@
 #![feature(in_band_lifetimes)]
 #![feature(macro_at_most_once_rep)]
 #![feature(inclusive_range_methods)]
+#![feature(extern_prelude)]
 
 #![recursion_limit="512"]
 

src/librustc/middle/expr_use_visitor.rs

@@ -32,7 +32,7 @@ use std::rc::Rc;
 use syntax::ast;
 use syntax::ptr::P;
 use syntax_pos::Span;
-use util::nodemap::ItemLocalSet;
+use util::nodemap::ItemLocalMap;
 
 ///////////////////////////////////////////////////////////////////////////
 // The Delegate trait
@@ -280,7 +280,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx, 'tcx> {
                param_env: ty::ParamEnv<'tcx>,
                region_scope_tree: &'a region::ScopeTree,
                tables: &'a ty::TypeckTables<'tcx>,
-               rvalue_promotable_map: Option<Lrc<ItemLocalSet>>)
+               rvalue_promotable_map: Option<Lrc<ItemLocalMap<ty::Promotability>>>)
                -> Self
     {
         ExprUseVisitor {

src/librustc/middle/mem_categorization.rs

@@ -87,7 +87,7 @@ use std::fmt;
 use std::hash::{Hash, Hasher};
 use rustc_data_structures::sync::Lrc;
 use std::rc::Rc;
-use util::nodemap::ItemLocalSet;
+use util::nodemap::ItemLocalMap;
 
 #[derive(Clone, Debug, PartialEq)]
 pub enum Categorization<'tcx> {
@@ -295,7 +295,7 @@ pub struct MemCategorizationContext<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
     pub tcx: TyCtxt<'a, 'gcx, 'tcx>,
     pub region_scope_tree: &'a region::ScopeTree,
     pub tables: &'a ty::TypeckTables<'tcx>,
-    rvalue_promotable_map: Option<Lrc<ItemLocalSet>>,
+    rvalue_promotable_map: Option<Lrc<ItemLocalMap<ty::Promotability>>>,
     infcx: Option<&'a InferCtxt<'a, 'gcx, 'tcx>>,
 }
 
@@ -404,7 +404,7 @@ impl<'a, 'tcx> MemCategorizationContext<'a, 'tcx, 'tcx> {
     pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                region_scope_tree: &'a region::ScopeTree,
                tables: &'a ty::TypeckTables<'tcx>,
-               rvalue_promotable_map: Option<Lrc<ItemLocalSet>>)
+               rvalue_promotable_map: Option<Lrc<ItemLocalMap<ty::Promotability>>>)
                -> MemCategorizationContext<'a, 'tcx, 'tcx> {
         MemCategorizationContext {
             tcx,
@@ -946,32 +946,35 @@ impl<'a, 'gcx, 'tcx> MemCategorizationContext<'a, 'gcx, 'tcx> {
             span,
             expr_ty,
         );
-        let promotable = self.rvalue_promotable_map.as_ref().map(|m| m.contains(&hir_id.local_id))
-                                                            .unwrap_or(false);
+        use ty::Promotability::*;
+        let promotability = self
+            .rvalue_promotable_map
+            .as_ref()
+            .and_then(|m| m.get(&hir_id.local_id).cloned())
+            .unwrap_or(NotPromotable);
 
         debug!(
             "cat_rvalue_node: promotable = {:?}",
-            promotable,
+            promotability,
         );
 
         // Always promote `[T; 0]` (even when e.g. borrowed mutably).
-        let promotable = match expr_ty.sty {
-            ty::TyArray(_, len) if len.assert_usize(self.tcx) == Some(0) => true,
-            _ => promotable,
+        let promotability = match expr_ty.sty {
+            ty::TyArray(_, len) if len.assert_usize(self.tcx) == Some(0) => Promotable,
+            _ => promotability,
         };
 
         debug!(
             "cat_rvalue_node: promotable = {:?} (2)",
-            promotable,
+            promotability,
         );
 
         // Compute maximum lifetime of this rvalue. This is 'static if
         // we can promote to a constant, otherwise equal to enclosing temp
         // lifetime.
-        let re = if promotable {
-            self.tcx.types.re_static
-        } else {
-            self.temporary_scope(hir_id.local_id)
+        let re = match promotability {
+            Promotable | NotInspectable => self.tcx.types.re_static,
+            NotPromotable => self.temporary_scope(hir_id.local_id),
         };
         let ret = self.cat_rvalue(hir_id, span, re, expr_ty);
         debug!("cat_rvalue_node ret {:?}", ret);

src/librustc/ty/mod.rs

@@ -2998,3 +2998,46 @@ impl fmt::Debug for SymbolName {
         fmt::Display::fmt(&self.name, fmt)
     }
 }
+
+impl_stable_hash_for!(enum self::Promotability {
+    Promotable,
+    NotInspectable,
+    NotPromotable
+});
+
+#[must_use]
+#[derive(Debug, PartialEq, Clone, RustcEncodable, RustcDecodable)]
+/// A fancy `bool` for making it less fragile to compute the promotability of something
+pub enum Promotability {
+    Promotable,
+    /// The value is promotable as long as that promotion will not cause parts of it to be inspected
+    /// at compile-time. So it can't be used in a BinOp or UnOp, or dereferenced, or...
+    NotInspectable,
+    NotPromotable
+}
+
+impl Promotability {
+    pub fn inspect(self) -> Self {
+        match self {
+            // We are allowed to promote operations inspecting the value on these
+            Promotability::Promotable => Promotability::Promotable,
+            // We are *not* allowed to inspect values of this
+            Promotability::NotInspectable => Promotability::NotPromotable,
+            // This isn't promoted anyway
+            Promotability::NotPromotable => Promotability::NotPromotable,
+        }
+    }
+}
+
+impl std::ops::BitAnd for Promotability {
+    type Output = Self;
+
+    fn bitand(self, rhs: Self) -> Self {
+        use self::Promotability::*;
+        match (self, rhs) {
+            (NotPromotable, _) | (_, NotPromotable) => NotPromotable,
+            (NotInspectable, _) | (_, NotInspectable) => NotInspectable,
+            (Promotable, Promotable) => Promotable,
+        }
+    }
+}

src/librustc/ty/query/config.rs

@@ -375,25 +375,6 @@ impl<'tcx> QueryDescription<'tcx> for queries::trait_of_item<'tcx> {
     }
 }
 
-impl<'tcx> QueryDescription<'tcx> for queries::const_is_rvalue_promotable_to_static<'tcx> {
-    fn describe(tcx: TyCtxt, def_id: DefId) -> String {
-        format!("const checking if rvalue is promotable to static `{}`",
-            tcx.item_path_str(def_id))
-    }
-
-    #[inline]
-    fn cache_on_disk(_: Self::Key) -> bool {
-        true
-    }
-
-    #[inline]
-    fn try_load_from_disk<'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
-                          id: SerializedDepNodeIndex)
-                          -> Option<Self::Value> {
-        tcx.queries.on_disk_cache.try_load_query_result(tcx, id)
-    }
-}
-
 impl<'tcx> QueryDescription<'tcx> for queries::rvalue_promotable_map<'tcx> {
     fn describe(tcx: TyCtxt, def_id: DefId) -> String {
         format!("checking which parts of `{}` are promotable to static",
@@ -842,7 +823,6 @@ macro_rules! impl_disk_cacheable_query(
 impl_disk_cacheable_query!(unsafety_check_result, |def_id| def_id.is_local());
 impl_disk_cacheable_query!(borrowck, |def_id| def_id.is_local());
 impl_disk_cacheable_query!(mir_borrowck, |def_id| def_id.is_local());
-impl_disk_cacheable_query!(mir_const_qualif, |def_id| def_id.is_local());
 impl_disk_cacheable_query!(check_match, |def_id| def_id.is_local());
 impl_disk_cacheable_query!(def_symbol_name, |_| true);
 impl_disk_cacheable_query!(type_of, |def_id| def_id.is_local());

src/librustc/ty/query/mod.rs

@@ -44,10 +44,9 @@ use traits::Clauses;
 use ty::{self, CrateInherentImpls, ParamEnvAnd, Ty, TyCtxt};
 use ty::steal::Steal;
 use ty::subst::Substs;
-use util::nodemap::{DefIdSet, DefIdMap, ItemLocalSet};
+use util::nodemap::{DefIdSet, DefIdMap, ItemLocalMap};
 use util::common::{ErrorReported};
 
-use rustc_data_structures::indexed_set::IdxSetBuf;
 use rustc_target::spec::PanicStrategy;
 use rustc_data_structures::indexed_vec::IndexVec;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
@@ -203,11 +202,6 @@ define_queries! { <'tcx>
         /// constructors.
         [] fn mir_keys: mir_keys(CrateNum) -> Lrc<DefIdSet>,
 
-        /// Maps DefId's that have an associated Mir to the result
-        /// of the MIR qualify_consts pass. The actual meaning of
-        /// the value isn't known except to the pass itself.
-        [] fn mir_const_qualif: MirConstQualif(DefId) -> (u8, Lrc<IdxSetBuf<mir::Local>>),
-
         /// Fetch the MIR for a given def-id right after it's built - this includes
         /// unreachable code.
         [] fn mir_built: MirBuilt(DefId) -> &'tcx Steal<mir::Mir<'tcx>>,
@@ -332,8 +326,8 @@ define_queries! { <'tcx>
 
     TypeChecking {
         [] fn trait_of_item: TraitOfItem(DefId) -> Option<DefId>,
-        [] fn const_is_rvalue_promotable_to_static: ConstIsRvaluePromotableToStatic(DefId) -> bool,
-        [] fn rvalue_promotable_map: RvaluePromotableMap(DefId) -> Lrc<ItemLocalSet>,
+        [] fn rvalue_promotable_map: RvaluePromotableMap(DefId)
+                                   -> Lrc<ItemLocalMap<ty::Promotability>>,
     },
 
     Codegen {

src/librustc/ty/query/on_disk_cache.rs

@@ -223,9 +223,7 @@ impl<'sess> OnDiskCache<'sess> {
                 encode_query_results::<unsafety_check_result, _>(tcx, enc, qri)?;
                 encode_query_results::<borrowck, _>(tcx, enc, qri)?;
                 encode_query_results::<mir_borrowck, _>(tcx, enc, qri)?;
-                encode_query_results::<mir_const_qualif, _>(tcx, enc, qri)?;
                 encode_query_results::<def_symbol_name, _>(tcx, enc, qri)?;
-                encode_query_results::<const_is_rvalue_promotable_to_static, _>(tcx, enc, qri)?;
                 encode_query_results::<symbol_name, _>(tcx, enc, qri)?;
                 encode_query_results::<check_match, _>(tcx, enc, qri)?;
                 encode_query_results::<codegen_fn_attrs, _>(tcx, enc, qri)?;

src/librustc/ty/query/plumbing.rs

@@ -1069,7 +1069,6 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
         },
         DepKind::PrivacyAccessLevels => { force!(privacy_access_levels, LOCAL_CRATE); }
         DepKind::MirBuilt => { force!(mir_built, def_id!()); }
-        DepKind::MirConstQualif => { force!(mir_const_qualif, def_id!()); }
         DepKind::MirConst => { force!(mir_const, def_id!()); }
         DepKind::MirValidated => { force!(mir_validated, def_id!()); }
         DepKind::MirOptimized => { force!(optimized_mir, def_id!()); }
@@ -1121,9 +1120,6 @@ pub fn force_from_dep_node<'a, 'gcx, 'lcx>(tcx: TyCtxt<'a, 'gcx, 'lcx>,
         DepKind::LookupDeprecationEntry => {
             force!(lookup_deprecation_entry, def_id!());
         }
-        DepKind::ConstIsRvaluePromotableToStatic => {
-            force!(const_is_rvalue_promotable_to_static, def_id!());
-        }
         DepKind::RvaluePromotableMap => { force!(rvalue_promotable_map, def_id!()); }
         DepKind::ImplParent => { force!(impl_parent, def_id!()); }
         DepKind::TraitOfItem => { force!(trait_of_item, def_id!()); }
@@ -1285,9 +1281,7 @@ impl_load_from_cache!(
     UnsafetyCheckResult => unsafety_check_result,
     BorrowCheck => borrowck,
     MirBorrowCheck => mir_borrowck,
-    MirConstQualif => mir_const_qualif,
     SymbolName => def_symbol_name,
-    ConstIsRvaluePromotableToStatic => const_is_rvalue_promotable_to_static,
     CheckMatch => check_match,
     TypeOfItem => type_of,
     GenericsOfItem => generics_of,

src/librustc_metadata/cstore_impl.rs

@@ -42,7 +42,6 @@ use syntax::edition::Edition;
 use syntax::parse::filemap_to_stream;
 use syntax::symbol::Symbol;
 use syntax_pos::{Span, NO_EXPANSION, FileName};
-use rustc_data_structures::indexed_set::IdxSetBuf;
 use rustc::hir;
 
 macro_rules! provide {
@@ -140,9 +139,6 @@ provide! { <'tcx> tcx, def_id, other, cdata,
 
         mir
     }
-    mir_const_qualif => {
-        (cdata.mir_const_qualif(def_id.index), Lrc::new(IdxSetBuf::new_empty(0)))
-    }
     fn_sig => { cdata.fn_sig(def_id.index, tcx) }
     inherent_impls => { Lrc::new(cdata.get_inherent_implementations_for_type(def_id.index)) }
     is_const_fn => { cdata.is_const_fn(def_id.index) }
@@ -164,9 +160,6 @@ provide! { <'tcx> tcx, def_id, other, cdata,
     rendered_const => { cdata.get_rendered_const(def_id.index) }
     impl_parent => { cdata.get_parent_impl(def_id.index) }
     trait_of_item => { cdata.get_trait_of_item(def_id.index) }
-    const_is_rvalue_promotable_to_static => {
-        cdata.const_is_rvalue_promotable_to_static(def_id.index)
-    }
     is_mir_available => { cdata.is_item_mir_available(def_id.index) }
 
     dylib_dependency_formats => { Lrc::new(cdata.get_dylib_dependency_formats()) }